Bolo (Pineapple) bun 菠蘿包

I really like this but have resisted making because it is so time intensive. I now finally have a Kitchenaid on the way (yay!) and I hope I can finally be able to make this. There are several version, notably the HK and Japanese version (called melon panメロンパン rather than pineapple; even tho neither contain any fruit!). What's the difference? I don't really know but I suspect the HK version is eaten with a big slab of butter (which I'll always remove) but the Japanese version  here the various recipes are for comparison.

HK method
- What's common about these methods is the use of Tangzong for the bread portion with milk powder, and kneading butter into the dough at the last stage like brioche.

1. Miki's Food
- Makes 6 buns
- Uses bread flour only.
- Cookie batter has no rising agent in the cookie batter, uses milk powder.
- Interesting: uses back of plate to flatten cookie dough rather than rolling out
- same method using air fryer

2. Dessert First Girl
- Makes 16 buns
- Mixes plain and bread dough. Uses custard powder.
- Butter is added at the last stage like brioche
- Cookie batter has bicarb of soda and baking soda with custard powder.

3. Yi Reservation
- Makes 10 buns
- This recipe uses bread maker
- Uses bread flour only. Uses milk powder.
- Cookie batter uses baking powder and ammonium bicarb to get the crackly effect with milk powder

4. Christine's recipes
- Makes 12 buns
- Uses bread flour only. Uses milk powder.
- Cookie batter uses evaporated milk, condensed milk, milk powder, together with ammonia powder and baking powder

Finally, a recipe without tangzong!
Omnivore's Cook - Tried below
- Makes 16 buns
- Mixes plain and bread dough. Uses heavy cream instead of tangzong. No milk powder, yay!
- Cookie batter uses both bicarb and baking soda, but an extra egg yolk
- Interesting way the cookie dough is made, by rolling into a log then cutting out discs before flattening it out

Japanese version
This is the only one I know by JOC. According to JOC, the HK version's cookie crust is less crispy or firm than the Jap version and flakes more easily. Bolo buns are also supposed to be fluffier and softer than Melon Pan.
- Makes 10 buns
- Mixes bread and cake flour
- Similar to HK method, butter is added at the final stage like brioche
- Cookie batter uses only baking powder
- The only recipe that uses stand mixer to mix the cookie dough

Ingredients (makes 16)
Cookie topping
60g (4 tbsp) butter, melted
4 tsp milk (*original recipe is 2 tsp: This has been slightly changed because I forgot the egg yolk and it was a good accident. The top was probably less rich but quite easy to work with and very crispy. Good change cos I hate having a leftover egg white anyway)
*1 egg yolk
½ tsp vanilla extract
140g (⅔C) sugar
150g (1C) flour
½ tsp baking powder
½ tsp baking soda
Pinch salt

Bread dough
200ml milk (180g or ¾C)
70g (⅓ C) sugar
2½ tsp yeast
160g (¾C) double cream
1 egg
300g (1¾C) bread flour
225g (1¾C) flour
1 tsp (5g) salt
3½tsp (50g) butter

Egg wash
2 eggs (original recipe: 2 yolks, 2 tsp milk)
½tsp sugar

Method
1) Prepare the cookie topping. Mix the butter, sugar, vanilla, milk, and salt until smooth.
2) In another bowl, sift the flour, baking soda and baking powder, and mix well.
3) Sift the flours into the cookie down and fold until well combined. Roll into a 5cm diameter log. Wrap in cling film and put in the fridge.
4) Prepare the bread dough. Warm the milk in the microwave until warm to the touch (about 40 deg C). Add the sugar and yeast and stir, and set aside.
5) In the stand mixer bowl, pour in the milk, double cream, flours. Attach the shield to prevent flour bombing. Use Speed 2 to stir until incorporated. Add the butter, kneading it into the dough with your hand. Use Speed 2 to mix, about 2 minutes. Use a spatula to scrape down if needed.

6) Turn up the mixer to Speed 4 and mix for 14 minutes, stopping occasionally to check elasticity. Stop when it passes the window pane test and the dough is smooth and shiny and leaves the bowl clean.
7) In the bowl, tuck the sides of the dough in until you get a smooth ball. Cover the bowl the cling film and leave to proof until doubled in size, about 1 hour.
8) Meanwhile, take out the log and slice into 16 equal discs. Flatten each disc in between two pieces of cling film with a pastry roller. Roll out to 6cm wide or 5mm thick. I've also seen a cook use a veggie cleaver to flatten it and scoop it up. I used a bench scraper to do the same.
9) Prepare 2 baking trays by lining with parchment. When the dough has sufficiently proved, divide into 16 portions (approx 62 to 65g; measure).
10) Roll each portion into a ball and tuck the ends underneath to form a nice ball.
11) Cover and leave to prove for 30 to 45mins until doubled in size. (If time permits, knock out the air, re-shape the balls, and leave to prove for another 30 to 45 mins)
12) Prepare the egg wash. It is easier to spread when cold so keep it refrigerated.
13) Use the bench scraper to transfer each cookie layer on the proved ball. Leave to prove for 15 minutes if time permits.
14) Brush each of the cookie layers with egg wash, twice so that a sufficiently thick layer coats it to give it that nice golden brown hue.
14) Bake at 176 deg C for 15 to 17 minutes until top is golden and bottom is slightly brown. I swapped the trays and turned them around halfway for a more even colour.

Recipe feedback
I forgot to include the egg yolk in the cookie dough and because it wouldn't come together, I added 2 tsp of milk instead to help it come together. The effect was that it wasn't very crumbly and a lot easier to work with. I haven't tried with the original yolk so have no idea whether it's very much harder to work with.

The next day, it had softened as expected but reheated by airfrying and it came out beautifully!